Common methods of sealing cartons or box blanks into cartons and boxes include hot melt gluing and taping. Taping can be costly, due to the amount of labor typically involved and the cost of the tape. Taping can also be unsuitable for use in continuous, high speed commercial carton or box blank assembly operations. Thus, many high speed commercial carton or box blank assembly operations utilize hot melt gluing techniques to close open ends of the cartons or boxes.
The use of typical inline hot melt application system can be problematic. A typical hot melt application system includes a reserve container for hot melt adhesive. The reserve container is heated to maintain a supply of hot melt adhesive when required. A supply tube extends from the reserve container to a nozzle positioned adjacent the assembly path of the carton. A pump selectively feeds the holt melt adhesive from the reserve container, through the supply tube, and to the nozzle. A valve prior to the nozzle exit selectively controls the feed of hot melt adhesive from the nozzle exit onto a passing carton.
The use of reserve containers to hold the melted glue requires the exertion of energy to heat the glue, as a larger than necessary quantity of glue must be kept at a melted temperature. Another draw back of hot melt applicators is the requirement of stocking hot melt pellets for feeding into the reserve container, which can also increase the amount of labor necessary to operate the carton assembly machinery.
The hot melt applicators apply hot melt to an unassembled carton while the carton is moving through the assembly and filling equipment at high speed, which can be at about 100-250 feet per minute. The high speed of the partially assembled carton, and inherent deviations of the carton from a preferred orientation, can result in a large margin of error in the placement of the hot melt. In order to compensate for the margin of error, a larger quantity of hot melt adhesive may be used than would be necessary if there was a reduced margin of error. The use of a larger quantity of hot melt adhesive can waste hot melt adhesive, thereby increasing costs of carton assembly, requires more energy to heat to the glue to the appropriate temperature, and can cool faster once applied to a carton.
Another problem with hot melt applicators, such as illustrated in FIG. 19, is that they require high maintenance. The hot melt application systems must be cleaned on a regular basis to prevent the build up of hot melt in the hot melt reserve container, supply line and, and in particular, nozzles. When hot melt builds up in the nozzle exits of the hot melt applicators, a decrease in the efficiency and a decrease in the accurate placement of the hot melt on a passing carton can occur. Inaccurate placement of the hot melt on a passing carton can cause alignment difficulties when the flaps are closed. For example, an inaccurately placed portion of typical hot melt adhesive can be too far inwardly from the outward edge of a flap. When that flap is pressed against an opposite flap, the outward edge may partially deflect the opposite flap, as illustrated in FIG. 11. In some circumstances, this can cause only a portion of the hot melt adhesive to be bonded to the opposite flap.
The use of typical hot melt adhesives can also lead to adhesion problems. When used to join carton flaps, a hot melt adhesive deposit is bonded on one side to one of the carton flaps and on the other side to the other one of the carton flaps. The holt melt adhesive may not achieve its full bonding strength to the carton flaps until long after the cartons have been filled and assembled, which can require the extended use of compression guides or other mechanisms to hold the carton flaps in the closed orientations for the hot melt adhesive to adequately set. In addition, when one side of the carton has a graphic printed thereon, the hot melt adhesive may not properly wet or diffuse into the printed portion of the carton, thus further increasing the time for adequate bonding of the hot melt adhesive to the carton flaps.